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I searched and searched and searched yesterday for an answer to the question "Does altitude affect AFUE?" but did not come up with any definitive answers. Hopefully this discussion will answer that…Continue

Attached is a spreadsheet I created for a restaurant client comparing two plans and projected kWh savings at 20% and 30%.Currently, they are on the rate plan "3B". If they were to remain on this plan…Continue

Does anyone else find the $300 membership fee a bit rich for a business consisting of only one self-employed owner?At $100 I might consider it, but at $300 they've pretty much prevented me from…Continue

Well I have to admit that I'm stumped with an energy audit I've been working on for the past two months. Perhaps someone can point me in the right direction...My client contacted me concerned that…Continue

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"Dale and I are referring to high efficiency condensing boilers designed to recover the latent heat of vaporization in a secondary heat exchanger designed for acidic condensate and capable of the highest combustion efficiency available in a gas-fired…"

"Yes,
They were trying to create a combustion system that could calibrate itself to the gas it it's burning and the air that it's supplied with. What interesting is how the addition of computer tech, software, and new hardware can simplify…"

"Dale, thanks for the info about "lambda sensor-free" burn calibration. This was news to me, and after researching it a while, this seems to be the way to go for a "plug-and-play" sort of combustion appliance for all altitudes."

"Morgan, I got this below from the Knight installation manual. I note a few things,
-These recommendations are not the "4% for every 1000 ft above 2000 ft" appropriate for natural draft boilers.
-They do indicate will derate itself 4% for…"

"Hans,
The car manufacturer's are doing it with mass flow sensors and oxygen sensors "lamda" sensors to operate the fuel injection and gas air mix, even dynamically as the car gains altitude.
Gas fuels are different from liquid or even…"

"I was trying to avoid naming manufacturers, but I was going by the published information for the smaller Knight boilers which use the "fire tube hx". Check me but I understood there was a derating schedule for these boilers.
Also note, the…"

"I look at this not about AFUE, but flue gas dewpoint. If your burn rate is rotting the heat exchanger then you have short life of heating system. Old school is about dewpoint - if natural gas flue products are at 130'F…"

"Though Viessmann is relatively unique in the application of Lambda technology to condensing boilers, most condensing boilers (I have installed 12 manufacturers) burning natural gas will not have to adjusted for altitude up to 6,000 feet or so.…"

"The heat exchanger gets burnt out, if presser is to high or if mix is to rich, then I see holes in the heat exchanger. I have done gas wells with low and high BTU content and have to test each one with 55 gal of Nat gas with some presser.…"

"Excellent reply Hans.
I think that there isnt' a good general answer to this question but that with anything but atmospheric equipment the manufacturers suggestions should be followed. The condensing boiler I've been working with for over…"

"Hans,Putting it the way you spelled it out so well helped me understand the whole process. So thanks also for your comments. I think this question has now been adequately answered! Thanks to everyone in this community. This website is full of…"

"Dale, I appreciate your comments, they make perfect sense. It seemed to me when I was researching this in the past that I came to the same conclusion as you, that it's actually possible the efficiency improves with altitude. Not sure I actually…"

"Rod,
Correct me if I am wrong, but you're saying "AFUE" but really mean "actual efficiency". AFUE is measured under controlled conditions in a lab at or near sea level, and has little in common with the actual efficiency…"

"Afue is not a real number. Look at system Efficiency BTU in vs BTU out, Its more real. Look at gas sold in boston most of east big citys are at 1050 BTU's per cub foot Kansas City is about 950-1050 …"

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